Dental alloys employed in the porcelain-fused-to-metal processing technique may be classified into several groups: gold based; palladium based; cobalt based and nickel based. The cost of the alloy is dependent upon the commodity prices of the alloy components. For example, as of December 2004, the cost of the major components of such alloys are: gold $442 per Troy ounce, palladium $183 per Troy ounce; cobalt $1 per Troy ounce; and nickel $0.3 per Troy ounce. The economic advantage of the base metals cobalt and nickel is obvious but the functional characteristics of the base metal alloys do not compare with those of the gold or palladium based dental products. In general, the base metal alloys are more difficult to cast, grind and bond to porcelain.
There have been numerous attempts to improve the functional characteristics of cobalt and nickel alloys through the addition of gold and the platinum group metals (the platinum group metals comprise platinum, palladium, rhodium, iridium, osmium and ruthenium).
Exemplary US patents describing such dental alloys:
U.S.PatenteepatentCommentsDavitz4,038,074Describes a nickel chromium alloy that may have 1 to 5 wt. % palladiumProsen4,253,869Describes a cobalt chromium alloy that may contain 7 to 15 wt. %rutheniumProsen4,255,190Describes a cobalt chromium alloy that may contain 1 to 5 wt. %ruthenium with gallium plus tungstenZwingmann4,382,909Describes a cobalt chromium alloy that may contain 1 to 70 wt. %palladiumPrasad4,459,263Describes a cobalt chromium alloy that may contain 5 to 15 wt. %rutheniumVuilleme6,613,275Describes a cobalt chromium alloy that may contain 0.5 to 4 wt. % goldPrasad6,656,420Describes an alloy that may contain 25 to 60 wt. % gold and up to 2wt. % ruthenium balance cobalt.Prasad6,756,012Describes a cobalt chromium alloy that may contain up to 20 wt. %platinum or palladium, up to 10 wt. % gold and up to 6 wt. % ruthenium
In each case, some improvement in the functional characteristics of the base metal alloy is achieved through the addition of gold and the platinum group metals. This invention expands the effort to improve the base metal based alloys through the judicious use of ruthenium additions in higher amounts than used in previous alloys.